Method and apparatus for adding fluid additives to fluids

ABSTRACT

An apparatus for adding an additive, such as a marker, to a base fluid, such as oil, includes a blender having a receptacle or diffusion chamber in which mixing of the additive and the base fluid occurs. The additive is injected in discrete amounts. Resistances to fluid flow in the receptacle or chamber cause fluid flow to occur at different rates in order to reduce the slugging effect caused by additive injection in discrete amounts.

The present invention relates to a method and apparatus for adding afluid additive to a fluid. The invention relates particularly, but notexclusively, to a method and apparatus for securely adding an additiveto fluid dispensed from a delivery means which is required to deliverfluid with and without an additive. The invention also relatesparticularly, but not exclusively, to a delivery means which is adelivery vehicle and to a method for securely adding marker chemical tomiddle distillate oils.

Many countries impose different rates of taxation on particular gradesof middle distillate oils. For example, diesel grade oil may be taxed ata relatively high rate when used for powering on-road vehicles, but beuntaxed or taxed at a lower rate when used for heating purposes, or forpowering off-road vehicles. Where such variations exist, it is necessaryfor the taxation authority to ensure that the untaxed or lower taxed oilcannot be used in circumstances where the higher tax rate should apply.Various methods have been used to meet this need. One method requiresthe users of higher taxed oil to keep records of distances travelled bymeans of a special meter and account for tax on this basis from time totime. Another more common method involves collecting the tax on thehigher taxed oil at source and chemically marking the untaxed or lowertaxed oil in order that any prohibited use can be readily detected.

Chemical marking usually takes place at the refinery or bulk storagedepot. It typically comprises two main components, a coloured dyemarking chemical which provides readily recognised marking on visualinspection and an invisible second marking chemical which is such moredifficult to remove than the dye chemical.

The use of chemical marker, or marker, has several advantages over themetering method. Firstly, it is more easily controlled. Secondly, iteliminates the need for special meters. Thirdly, it eliminates the needto record and account for distances travelled. Fourthly, it taxes fuelconsumption rather than distance travelled and therefore encourages fuelefficiency.

However, it has the relative disadvantage that the same delivery vehiclewill not normally be able to deliver both marked and unmarked oil wherethe oil is stored in a common tank on the vehicle. This arises becausethe systems available for the addition of marker are unlikely to besufficiently secure to be accepted by the taxation authorities. Forexample, with systems which are currently available, a dishonestoperator could deliver unmarked oil but record it as marked and therebyavoid payment of the higher tax by either disabling the marker system orby replacing the marker with a different fluid. Throughout thisspecification, the term secure refers to an acceptable level ofprevention of tampering or unauthorised interference.

The requirement to use different delivery vehicles for marked andunmarked oil may increase costs in several ways. Firstly, it maynecessitate the need for larger numbers of delivery vehicles. Secondly,it may necessitate additional distances travelled in situations whereone destination or route could be delivered by one vehicle if it coulddeliver both types.

An object of the invention is to overcome these disadvantages byproviding a se cure system which c an add marker at the point ofdelivery and thus allow one vehicle to deliver both marked and unmarkedtypes.

It is noted that the disadvantages associated with current systems wouldnot be adequately overcome by using a delivery vehicle with two or moretank compartments, separately containing marked oil and unmarked oil,for the following reasons. Firstly it may be troublesome to attempt tomatch the relative quantities for marked and unmarked oil on the vehiclewith the relative quantities required for its delivery schedule. Therelative quantities may not even be known in advance. Also, quantitiescan only be carried in discrete tank sized amounts. Secondly, changingtank use from marked to unmarked use may necessitate frequent cleaningof the tanks, which would be time consuming and costly, and would carrythe risk of residual marker contaminating the unmarked oil. Thirdly,where the risk of cross contamination prevented sharing of deliveryequipment for marked and unmarked oils, carrying the additional type ofoil would further increase costs because it would necessitate equippingthe vehicle with an additional pump and flowmeter.

The possibility of cross contamination from shared delivery equipment isalso important in the general case of a delivery vehicle with a largernumber of separate compartments holding the same basic fluid but withdifferent additives. Such vehicles frequently measure quantitiesdelivered by means of simple dipsticks because a common flowmeter cannotbe used due to the possibility of cross contamination and it would betoo expensive to provide flowmeters on every compartment. Measurement bydipstick is costly in labour and can be difficult in poor weatherconditions. A further object of the invention is to overcome thisdisadvantage by providing a secure system which can add additive at thepoint of delivery and thus allow a range of fluid and additive mixturesto be delivered by common equipment, including a flowmeter, without riskof cross contamination.

Additive injection is used to inject fluid additives into base fluids inmeasured proportions. Reciprocating injection pumps, or injectors, arecommonly used as dosing pumps in apparatus used for additive injection.

The injector typically comprises a piston and cylinder arrangement whichis provided with an inlet check valve and outlet check valve and a meansfor reciprocating the piston in the cylinder. When the piston is drawnback in the cylinder, the negative pressure differential created in thecylinder causes the inlet check valve to open and the outlet valve toclose or remain closed and additive is drawn into the cylinder throughthe inlet pipe. When the piston returns in the cylinder, the positivepressure differential created causes the inlet valve to close or remainclosed and the outlet valve to open and additive is expelled from thecylinder into the outlet pipe. This process is repeated at each cycle ofthe injector.

The reciprocating means can be provided in several different ways, avery common means being by the use of a pneumatic piston and cylinderactuator which has its piston coaxial with and linked to the piston ofthe injector. The pneumatic actuator piston may be reciprocated byconventional pneumatic control means which in turn reciprocates theinjector piston. Other examples of reciprocating means include springreturned pneumatic actuators and mechanical eccentric cams driven byrotating means.

Where a pneumatic actuator is used, the operation of the injectoractuator and pump will usually be triggered by a pulse or signal from adevice associated with a flow meter measuring the flow of base fluid andwhich will cause the injector to carry out one reciprocating cyclecomprising a suction and delivery stroke. If the pulse or signal fromthe device is arranged such that it occurs each time a set proportion ofbase fluid passes the flow meter, then the flow of additive pumped bythe injector will be proportional to the flow of base fluid. Thereciprocating cycle is conventionally seen to have a characteristiclength of time for each injector which will determine the maximum rateat which the injector can be run.

Usually some means is provided whereby the volume displaced at eachstroke of the injector piston can be varied by varying the length of thepiston stroke. Where a pneumatic actuator is used, this variation isfrequently provided by a threaded adjustment member which acts as a stopwhich limits the length of the piston stroke in one direction. Thisvariation allows the pump to be calibrated subsequent to manufacture.

The accuracy of injectors of the type described above, across the rangeof working pressures, can vary up to about ±5%. Where greater accuracyis required, other means are frequently used, such as proportionalmetering valve arrangements with,direct flow meter control which canreadily give absolute accuracies across the range of working pressureswithin ±0.5%. The metering valve arrangement has the disadvantage thatit is usually more complicated and expensive than an injector.

Injectors can also have the disadvantage that they do not mix additiveevenly into the base fluid but inject discrete amounts of additive intoa continuous stream of base fluid. This intermittent mixing method,sometimes referred to as slugging, gives rise to two potential problems.Firstly, the injected stream comprising additive and base fluid does notinitially form an even mixture. Secondly, where small batch quantitiesare taken from the uneven mixture, the overall resulting proportions maybe significantly incorrect and cannot be rectified by subsequent mixingof the batch quantities.

It is also an object of the present invention to provide apparatus whichreduces the slugging problems which can arise from the uneven mixture ofadditive and base fluid caused by the injection method. It is a furtherobject of the present invention to provide apparatus which can providemuch improved accuracy in relation to the proportion of additiveinjected into the base fluid.

The invention is defined in the appended claims 1 to 49 which areincorporated into this description by reference.

The invention will now be described more particularly with reference tothe accompanying drawings which show, by way of example only, anembodiment of the invention which is suitable as an apparatus forsecurely adding marker chemical to middle distillate oils dispensed froma delivery vehicle which is required to deliver oil with and without themarker.

FIG. 1 shows, in diagrammatic form, the delivery and control apparatuson a delivery vehicle, with electronic, electric or pneumatic controllines shown as dashed lines;

FIG. 2 shows, again in diagrammatic form, a view of part of the deliveryand control apparatus shown in FIG. 1 in more detail and on a largerscale; and

FIG. 3 shows a diagrammatic and simplified view of an injector with apneumatic actuator provided with directional and speed control valves.The injector and pneumatic actuators are shown in section.

The following is an index of the reference numerals used in the figures:

1 Oil tank

2 Oil pump

3 Oil flow meter

4 Two-way valve

5 Unmarked oil delivery pipe

6 Marked oil delivery pipe

7 Marker tank

8 Marker level sensor

9 Marker low flow sensor

10 Injector or injector pump

11 Cabinet

12 Pulser unit

13 Electronic control and recording means or controller

14 Cab warning indicator

15 Marker tank, upper section

16 Cabinet access sensor

17 Marker tank, lower section

18 Anti flush section

19 Anti flush retarding means

20 Anti flush outlet pipe

21 Blender

22 Blender diffusion chamber

23 Blender oil inlet

24 Blender marker inlet

25 Blender outlet

26 Blender manifold

27 Blender manifold openings

28 Injector body

29 Cylinder

30 Piston

31 Cylinder cavity

32 Injector outlet

33 Outlet check valve

34 Injector inlet

35 Inlet check valve

36 Actuator

37 Actuator body

38 Actuator cylinder

39 Actuator piston

40 Link rod

41 Actuator cylinder cavity

42 Actuator port

43 Directional control valve

44 Restrictor check valve arrangement

45 Adjustment member

46 Adjustment member lock nut

Referring now to FIGS. 1 and 2, there is shown a delivery vehicle oiltank 1 of unmarked oil which may comprise one or a plurality ofinterlinked compartments. Oil is pumped from the tank 1, by an oil pump2 through an oil flow meter 3 to a two-way valve 4 connected to one oftwo delivery pipes, an unmarked oil delivery pipe 5 and a marked oildelivery pipe 6.

The marked oil delivery pipe 6 is connected to a marker system whichsecurely and automatically adds marker in the desired proportion to oil.The marker system comprises a marker reservoir or tank 7 with an uppersection and a lower section, the sections being connected by a shortpipe section in which a marker level sensor 8 is mounted. The markertank comprises a further anti-flush section 18 below the lower sectionof the tank. Marker flows by gravity feed along a marker pipe to aninjector unit 10 which pumps marker in the desired proportion into themarked oil delivery pipe 6. The injector unit 10 comprises a fixedstroke piston pump which delivers a set volume of marker when signalledby an electric or pneumatic pulse.

The anti flush section 18 is fitted with retarding means 19, whichcontrol and retard flow within the section 18, and with anti drainingmeans, such as an outlet pipe 20 which has its entry in the upper regionof the section 18. The retarding means 19 may comprise, for example, anumber of perforated baffles or one or more perforated receptacles.

The marker pipe is provided with a marker low flow sensor 9.

The marker tank 7 and all the components of the marker system down tothe marked oil delivery pipe 6, including the adjacent section of markedoil delivery pipe 6 are contained within a secure cabinet 11. Thecabinet comprises a door with a lock and also comprises a cabinet accesssensor 16 which signals if access is made to the cabinet.

A pulser unit 12 is attached to the flow meter 3 and generates pulses inproportion to the flow of oil through the flow meter 3.

The apparatus is also provided with an electronic control and recordingdevice 13, henceforth referred to as the controller 13, which isconnected by electronic, electric or pneumatic signal lines to themarker level sensor 8, the marker low flow sensor 9, the cabinet accesssensor 16, the two-way valve 4, the injector unit 10, the pulser unit 12and a cab warning indicator 14, such as a lamp, in the vehicle cab.

The apparatus is additionally provided with a printer which produces acustomer coupon which states the quantity of oil delivered andidentifies whether it is marked or unmarked oil. In one variation, theprinter is an electronically controlled type connected to the controller13. In another variation, it is a mechanical type connected directly tothe oil flow meter 3.

Flow meters with printers and injector units with associated pulserunits for adding additives to fluids at the point of delivery are allwell known and widely used on delivery vehicles. Electronic control andrecording devices of various types are also well known and widely usedon delivery vehicles.

The marker level sensor 8 and marker low flow sensor 9 may, for example,comprise electronic proximity switches or electronic reed switches. Themarker level sensor may comprise a metal or magnetic float in the tankrestriction which is sensed by the electronic switch. The marker lowflow sensor may comprise a metal or magnetic part which is liftedagainst gravity in a vertical tube by the flow pulse and which is sensedby the electronic switch. The cabinet access sensor 16 may beconveniently provided without the need for an additional electronicswitch by arranging the wiring from some or all of the other sensors topass through a coupling, such as a multi-pin plug and socket coupling,which is geometrically situated such that it must be disconnected togain access into the cabinet 11. The controller 13, can be arranged todetect and record when the coupling is opened by monitoring the circuitsconnected through the coupling. The two-way valve 4 may comprise two airoperated valves which are solenoid controlled by signals from thecontroller 13. The operation of the particular embodiment of theinvention will now be described.

Many of the elements involved in delivering marked and unmarked oil aresimilar to those used in various combinations in the known art for thedelivery of fluids with or without an additive where the system does notrequire a high level of security. In these known elements, the two-wayvalve 4 directs the pumped fluid, oil, into one of two separate deliverypipes 5,6 as appropriate. Additive, marker, fed from a storage tank 7 onthe vehicle, is injected into the relevant delivery pipe 6 in proportionto the quantity of oil delivered through the pipe 6 by means of theinjector unit 10 controlled by the controller 13 and pulser unit 12associated with the flow meter 3. A coupon is printed and an electronicrecord of the delivery made by the controller 13 by means of signalsfrom the pulser unit 12 and the two-way valve 4.

The particular embodiment of the invention includes the followingadditional elements which are not known in the relevant prior art.

The marker tank 7 is divided into two sections 15, 17 joined by a narrowconstriction fitted with a marker level sensor 8. The volume of theupper section 15 corresponds to the standard refill volume, which istypically about 25 liters where marker concentration is about 100 partsper million. The base of the upper section 15 is sloped towards theentry to the constriction in order to ensure that no residual markerremains in the upper section when the level in the tank falls to thelevel of the marker level sensor 8. The volume of the lower section 17corresponds to the quantity of marker considered necessary to act as areserve to provide marked oil in the interim period between the driverbeing alerted by a signal associated with the operation of the markerlevel sensor 8 and the tank being refilled with marker. The volume ofthe lower section 17 may be made relatively large if the possibility ordesirability of long interval periods is envisaged. However, the lowersection 17 should not be larger than the upper section 15, because asingle standard refill might otherwise not reach the level of the markerlevel sensor 8.

Positioning the marker level sensor 8 in the constriction between thetwo tank sections 15, 17 increases its accuracy in two ways. Firstly, itmeasures the level where the cross sectional area is small and a smalldifference in volume causes a relatively large difference in level.Secondly, its operation is no longer measurably affected by variableinclination of the delivery vehicle and its equipment.

When the marker in the tank 7 falls to the level of the marker levelsensor 8, the sensor 8 signals the controller 13 and the event iselectronically recorded and a warning indicator 14, such as a lamp inthe vehicle cab, remains activated until the marker tank 7 is refilled.The driver will arrange for the marker tank 7 to be refilled during asubsequent visit to the depot where replacement marker is stored.

The tank 7 is always refilled with a defined and accurately controlledquantity of marker. Consistent and tamper resistant refill quantitiescan be assured in several ways. The refill quantity can be taken from abulk tank of marker at the depot using a device which will accuratelydispense the required defined quantity or alternatively it can be takenfrom one or a set number of accurately filled containers of marker.

The controller automatically prepares electronic summarised records ofall deliveries in chronological sequence, distinguishing between markedand unmarked deliveries, and simultaneously accurately records realusage of marker related to marked deliveries. Any irregularities areautomatically analysed and signalled. The resulting records can be usedfor legal purposes, spot checks, audits, general statistics orhistorical checking of suspected blocks of deliveries. Usually therecords will not be disclosed to the vehicle operator or driver but willbe monitored and stored at a centralised base.

The recorded information allows immediate and subsequent audits orchecks to be made to compare the actual proportion of marker added tothe oil against the set standard because the known refill quantity isthe amount used between operations of the marker level sensor. Thecontroller 13 automatically checks the proportion and indicates if it isnot within acceptable tolerances.

The proportions of marker to oil can thus be very accurately calculatedeach time the level in the upper tank section falls to the level of themarker level sensor. This information can also be used to calibrate orrecalculate the stroke capacity of the injector pump, since the numberof injector strokes which occurred as the defined quantity of marker wasused can be recorded. A constant self calibration of the injector pumpcan be automatically carried out by the controller by this means. Thisallows a count of the injector pump strokes to be used as a reasonablyaccurate measure of the amount of marker used between operations of themarker level sensor and thereby provides the controller with aconvenient and accurate means to provide a measure of markerconcentration, marker usage and marker stock levels at all times.

The marker low flow sensor 9 is used to ensure that oil is notaccidentally or deliberately dispensed through the marked oil deliverypipe 6 without the addition of marker.

If any of the sensors detects an abnormal condition, the event isrecorded by the controller which will take appropriate action. Thisaction may include disabling of the dispensing system or activation ofsystems which are available to alert the central base.

The anti flush section 18 is used as a further safeguard to preventintermittent replacement of marker by a spurious fluid such as unmarkedoil or oil which contains a transient or easily removed dye, or bymarker without the invisible second marking chemical. For example,gaining unauthorised access to the cabinet 11 and overriding ordisabling the signals from the relevant sensors could allow replacementof the marker by an equal quantity of spurious fluid and visa versa.This deception would not be detected by the marker low flow sensor 9 orby the apparent proportion of marker to marked oil which would berecorded by the controller 13.

The anti flush section 18 contains a significant quantity of marker andis constructed in a way such that it is very difficult to quickly removeall or a significant portion of its contents. The outlet pipe 20prevents the contents of the section 18 being drained or being blown outunder pressure. The retarding means 19 prevent the main body of markerbeing quickly flushed out by flushing spurious fluid through the deviceas the flushing fluid will largely short circuit from the inlet to theoutlet of the section 18 and little will reach the inner sections of thesection 18. The section 18 is arranged such that air can freely ventupwards when the marker tank is filled. The particular embodimentincludes retarding means 19 which comprise one or more horizontalperforated separation baffles.

The apparatus is made subject to periodic spot checks to ensure that ithas not been tampered with and that the correct type of marker is beingused. Where possible, the apparatus is arranged or constructed in amanner which will show up any alterations or unauthorised interference.

It is also important that the security system prevents illicit switchingof either the electronic or pnuematic control signals to the two-wayvalve, as this would otherwise allow an oil delivery to take place whichwas recorded as marked, with marker being injected into the markeddelivery pipe, but with unmarked oil actually being delivered throughthe unmarked pipe. In one embodiment of the invention, the two-way valveis also enclosed within a secure cabinet and the two-way valve andinjection system are pneumatically and electrically interlocked withinthe cabinet preventing the injection system being operated unless theunmarked oil port of the two-way valve is closed and the marked oil portis open.

Where the two-way valve 5 comprises two air operated valves which aresolenoid valve controlled by signals from the controller 13, and wheremarker is added by an air operated injector pump which is also solenoidvalve controlled, the interlocking may, for example, be achieved by thefollowing means. The air supply to the injector pump is taken from thesupply which opens the air operated valve port supplying marked oil.This prevents the injector pump being operated when the marked oil valveport is not opened. An air pressure switch, with normally closedelectrical contacts, is connected to the air supply which opens the airoperated valve port supplying unmarked oil, and the electrical signal tothe injector pump solenoid is wired through it. This again prevents theinjector pump being operated when the unmarked oil valve port is opened.The solenoid valves, the pressure switch and the interconnections, areall located within the secure cabinet.

In a preferred embodiment, not shown in the figures, the two way valveis enclosed within the same cabinet as the marker tanks and theinjection system. The cabinet is of rectangular shape with the tanks andanti flush section occupying one end and sharing common walls with thecabinet. The two-way valve occupies the other end of the cabinet withthe oil delivery inlet entering a side wall of the cabinet and the twooil delivery outlets exiting through the top of the cabinet. Theinjection system occupies a generally central position in the cabinet.This arrangement can be made sufficiently small to fit at low levelbetween the chassis members of a typical oil delivery vehicle. In onearrangement the external dimensions of the cabinet are 400 mm in height,500 mm in width and 650 mm in length. An arrangement of this type hasseveral potential advantages. Firstly, the cabinet is well protectedfrom crash damage and consequent danger of spillage of the markerchemical. Secondly, the marker chemical is stored and refilled at a safelow level. Thirdly, the single cabinet arrangement allows most of thepipework and electrical connections to be prepared and tested beforebeing fitted to the vehicle.

Other variations of marker reservoir 7 and means to detect the rate atwhich marker is replaced may be used in effecting the apparatus of theinvention. For example, the reservoir 7 may comprise one or morecontainers of marker linked to the apparatus. The audit or check tocompare the actual proportion of additive added to the fluid against setstandards may also be made by securely counting or recording theoccurrence of various events associated with the filling, depletion,replacement or connection of container or tank reservoirs 7.

Various types of electronic control and recording means, are used ontanker vehicles which deliver oil or other fluid products. Theyfrequently comprise an electronic controller or a computer in thevehicle cab used in conjunction with an electronic flow control device,hereafter referred to as a flow counter, pulsed from a flow measurementdevice on the oil delivery line. Vehicle computers are usually termedOTCS, or on-truck-computers. The flow counter or electronic controllerusually comprises a small programmable logic unit and typically includesa memory device such as an erasable programmable read-only memory orEPROM device. The OTC usually compiles the electronic record of thedeliveries and other relevant information and this record is retrievedby various means for subsequent checking and storage.

A problem which arises from the use of an OTC where additive must besecurely added on a delivery vehicle is that it is very difficult toprevent the possibility of dishonest operators reprogramming or hackinginto the software system to manipulate the record or calculation ofadditive concentration. OTC systems are very similar to ordinarypersonal computer systems and a wide cross section of people arefamiliar with their operation and manipulation. It is an object of thepresent invention to overcome or reduce this problem.

The present invention provides various means which prevent reprogrammingor hacking into the flow counter or controller software. These meansinclude apparatus which physically denies access required forreprogramming or hacking into the flow counter or controller by the useof a mechanical or electronic locking means or by means of a sealingmeans, sometimes used in conjunction with an enclosure means whichisolates one or more memory devices comprising the flow counter orcontroller and to which access must be gained in order to modify ordisable the security system. The enclosure means may comprise a securecasing with a lockable or sealable opening. The locking means may, forexample, comprise a key operated locking device. The sealing means may,for example, comprise encapsulation in a sealing material such as resinor fixing with a wire and lead tag.

The present invention also includes detection means which monitorphysical access to or removal of one or more memory devices comprisingthe flow counter or controller which permits reprogramming or hacking tobe carried out. The security system is activated if illicit access orremoval is detected. The detection means may, for example, comprise anormally live circuit within the memory devices or some part of the flowcounter or controller which is arranged such that it is broken if therelevant physical access to or removal to permit reprogramming orhacking takes place. The detection means may also, for example, comprisean electronic or electric sensor which is activated if the relevantphysical access to or removal to permit reprogramming or hacking takesplace.

Isolation of the flow counter or controller memory devices can beachieved in ways that are not possible with a computer such as an OTC.Unlike a computer or OTC, the memory devices normally cannot bereprogrammed or hacked into using the operational external input oroutput wires or terminals. Also, the memory devices are very muchsmaller than an OTC and have no operator interfaces such as screens orkeyboards, which accordingly allows them to be readily encapsulated orenclosed in a secure casing.

The present invention also provides for one or more of the memorydevices comprising the flow counter or controller to be replaced bymemory devices which cannot be reprogrammed. An OTP orone-time-programmable device is an example of such a memory device.

The present invention additionally provides for part of the securitysystem to be duplicated on the OTC and on the electronic flow counter orcontroller. If either system detects illicit manipulation, it willindependently activate a security system, such as shutting down thetruck delivery system, marking an electronic record or alerting thecentral base. Usually the electronic flow counter or controller willhave more limited programmable capacity than the OTC and will thereforeoperate a simpler security system than the OTC. However, the inventionmay also be used on trucks without OTCS.

Returning to FIGS. 1 and 2, the apparatus is also provided with ablending means or blender 21 connected to the delivery pipe 6. Theblender 21 includes a manifold 26 and a receptacle or diffusion chamber22. The diffusion chamber 22 may comprise an elongate tube. The injectoroutlet pipe 32 communicates with the manifold 26 through a short lengthof pipe which is connected through a marker inlet 24 to the manifoldgallery which in turn communicates with the diffusion chamber through arow of holes or openings 27 along the upper surface of the manifold 26.The diffusion chamber communicates with the delivery pipe 6 through ablender base fluid inlet 23 at one end and a blender outlet 25 at theother end. The blender 21 is positioned below the delivery pipe 6 and atan inclined angle to prevent air entrapment and to prevent leakage ofthe mixture of oil and marker from the diffusion chamber 22 into thedelivery pipe 6 between deliveries. The manifold 26 is also arrangedwith the manifold openings 27 on its upper surface so that additive isretained in the manifold between deliveries. The blender inlet 23 andoutlet 25 pipes are raised in the delivery pipe 6 to prevent ingress ofsludge or debris and are provided with oblique openings facingrespectively upstream and downstream in the delivery pipe 6. Althoughnot shown in the figures, the outlet pipe 25 may be advantageouslyterminated with a bend such that the axis of the pipe end is alignedwith the axis of the delivery pipe and its opening faces downstream.This will help to reduce local turbulence and promote more even flowfrom the outlet pipe 25. The relative flow of oil through the diffusionchamber 22 is regulated by a restriction in the outlet 25 pipe which isalso not shown in the figures.

The inlet 23 pipe is deliberately arranged with very little resistancein order that the greater part of the flow surge which occurs wheninjection takes place, flows backwards through the inlet 23, thuspreventing a slug of oil-marker mixture being displaced into thedelivery pipe 6. The backward flow through the inlet 23 into thedelivery pipe comprises oil without marker. As oil flows in the deliverypipe 6, a pressure differential is created between the two openings 23,25 of the diffusion chamber 22 which causes flow within it, but at alower speed. The speed may be set by suitable arrangement of therestriction.

Additive injected into the diffusion chamber 22 mixes with base fluidalong the manifold 26 to form an elongated body of mixed or partly mixedfluid, and the outlet 25 in the diffusion chamber 22 is restricted toregulate the flow and relative speed of fluid passing through thediffusion chamber 22 to ensure that there is overlap between successiveelongated bodies passing through the diffusion chamber 22. This ensuresthat a substantially continuous stream of mixed fluid enters thedelivery pipe 6 from the blender outlet 25 of the diffusion chamber 22.

It is sometimes advantageous to ensure that additive is not removed fromthe manifold 26 when injection is not taking place either by the passageof oil over the openings 27 or by pressure differentials set up withinthe diffusion chamber 22 which could cause oil to enter some of theopenings 27 in the manifold 26 and displace additive through openings 27where the fluid is at a lower pressure. Such removal of additive shallhenceforth be referred to as scouring. Scouring will give rise toreduced accuracy in the proportion of oil and additive in that thescoured additive will increase the concentration when scoured but willreduce the concentration at the following injection as the manifold 26will require to be replenished. When scouring occurs, its effects willbe variable due to variations in the flow of oil in the delivery pipe 6and to factors such as temperature influenced viscosity effects.

The possibility of scouring is reduced or prevented by various means.These include avoiding severe irregularities or resistances in thediffusion chamber 22 which might give rise to pressure differentialsalong the manifold 26. In particular, where a diffusion chamber 22 ofthe type described in the preferred embodiment is used with a singlemanifold 26, the flow restrictors should be either upstream ordownstream of the manifold. Scouring is also reduced or eliminated byarranging the manifold openings 27 to be of small cross sectional areaand to be of length which is relatively long in proportion to theirwidth. For example, a manifold 26 of around 150 mm to 200 mm in lengthmay be provided with about 6 holes of diameter 1 mm and depth 10 mm. Itis important to ensure that the injector pump 10 develops sufficientpressure in the additive to allow it to pass through the holes withinthe allowable time cycle and that the additive is not of a type whichwill clog small passageways. Alternatively, scouring can be reduced orminimized by providing small check valves in the manifold 26. Forexample, if the manifold 26 gallery is fed from the centre, a checkvalve may be placed in each section of the gallery to prevent backwardsflow and thereby prevent internal circulation between its two sections.Alternatively, the manifold 26 may comprise manifold openings 27 whereeach is provided with a separate check valve.

The effect of any scouring which might accidently occur is minimised byreducing the quantity of additive contained in the manifold. This isachieved by ensuring that the connecting passages and galleries to themanifold 27 openings are not made larger than is required for theoperation of the injector pump 10 within the allowable time cycle or isnecessitated by the manufacturing process.

When regulating the rate of flow in the diffusion chamber 22 to set thedegree of overlapping of the elongated bodies, a compromise must bereached. On the one hand, reducing the flow will give a greater degreeof overlapping and consequently a more homogeneous mixing in thediffusion chamber 22. On the other hand, reducing the flow andincreasing the degree of overlapping will increase the averageconcentration of marker in the oil in the diffusion chamber 22. Thiswill have the potential drawback of increasing any problems of fluidexpelled from the diffusion chamber 22 by the injection stroke orproblems of leakage between the diffusion chamber 22 and the deliverypipe 6 between deliveries. In practice a rate of flow which causes oneto three overlaps of the elongated bodies has been found satisfactory.

The use of manifold openings or outlet holes 27 of small diameter andrelatively long length has advantages in addition to preventing orminimising scouring or leakage of marker into the diffusion tube 22 whenthe system is out of operation. The small holes lengthen the time periodof injection and thereby assist the formation of the elongated bodiesand reduce the effect of fluid being expelled from the diffusion chamber22 during injection. The small holes also help to ensure even flowthrough each of the manifold openings or holes 27 during injection.

The blending means 21 reduces or eliminates the problems andinaccuracies which arise from slugging where shots of additive areinjected into the continuous stream of oil. If not otherwise dealt with,the oil and additive mixture delivered into the delivery line wouldcomprise alternating quantities of marked and unmarked oil. Althoughthese alternating quantities would usually mix together in the storagetank into which they are delivered, if a small quantity of oil andadditive mixture is delivered or if a small sample is taken forexamination, the proportion of additive in the mixture would most likelybe incorrect. Slugging also gives rise to a potential security problemin that it is possible to separate the marked and unmarked quantities ofoil passing down the delivery line by connecting a length of transparenthose to the end of the line and manually switching the hose end betweentwo tanks as the oil alternates between marked and unmarked. Switchingcould also be achieved without the use of a transparent hose by initialobservation of the outflowing oil and then using the noise of theinjector pump 10 when the appropriate sequence pattern becomes clear. Ineither of these cases it is possible for the operator to reduce the flowfrom the hose end and thereby increase the interval time betweeninjection pulses. Switching could also be achieved automatically using aphotocell controlling a change-over valve, in which case the deceptioncould be achieved by the recipient without the delivery operator beingaware that it was taking place. Slugging also gives rise to a potentialproblem where the marker or additive is of a corrosive nature. Thisconcerns the possibility of damage to ordinary hose and seal materialswhere dispensing hoses and seals are left with concentrated localisedslugs of marker over prolonged periods.

In most cases the effectiveness of the blending means 21 is increased byany mixing which takes place between additive and base fluid within theblending means 21 or the diffusion chamber 22 for reasons which includethe following. Firstly, well mixed fluid within the blending means 21 ordiffusion chamber 22 will promote more even dispersion in the deliverymeans 6 as it gradually flows into it. Secondly, any quantity of fluidwhich might be displaced into the delivery means 6, when additive isinjected into the diffusion chamber 22, should ideally comprise a wellmixed and diluted combination of additive and base fluid to minimiseslugging effects. The blending means 21 may be geometrically arrangedsuch that injection of additive creates turbulence within the blendingmeans 21 to increase mixing within it. The blending means 21 may also beprovided with baffles or irregularities to increase mixing as theadditive and base fluid pass through it.

The blending means 21 may be arranged in various other ways and thesuitability of different variations may depend on the flow of basefluid, the proportion of additive injected, the rate of injection andthe viscosities and miscibilities of the two fluids. In some cases themanifold 26 may be omitted from the diffusion chamber and injection takeplace from an outlet with mixing occurring within the chamber 22 byother means including turbulence.

The blending means 21 may also comprise arrangements which do notinclude a manifold 26 but where injection occurs at different outlets oropenings in the blending means or in the delivery means 6.

The blending means 21 may additionally comprise the deliberate slowingdown of the injection stroke. This can be achieved by several meansincluding arranging the injection opening or manifold openings 27 to beof small cross section, or by restricting the exhaust of the actuatorwhere the injector 10 is driven by an air actuator 36. Slowing down ofthe injection stroke can give rise to several benefits. Firstly, it willhelp to spread the slug as it is injected into the base fluid. Secondly,it will reduce fluid and mechanical shock within the injection system byreducing the velocity of the moving parts of the injector pump and thevelocity of the fluid. Thirdly, it may reduce any momentary effects onfluid velocity within the blender diffusion chamber which mightotherwise cause an uneven flow rate from the blender into the deliverypipe.

The blending means 21 may also comprise one or more injection points oran injection manifold 26 located in a section of a delivery means 6,where flow speed is reduced by increasing the relative cross sectionalarea.

The blending means 21 may also be located in the delivery means 6downstream of the injection position. In this instance the flow in thedelivery means 6 is divided into separate receptacles or channels withdifferent resistances to flow, such that individual quantities of theseparate flows are staggered or spaced apart as they come together againin the delivery means 6. Thus, a slug of additive moving in the streamof base fluid will be broken into several smaller spaced apart slugs ofadditive. The overall cross sectional area of flow may be increased tocompensate for the lower flow rates in the restricted channels. Thecross section of individual channels or groups of channels may beincreased in proportion to the resistance to flow to allow even sizingand separation of the smaller slugs.

The blending means 21 may be used with a wide variety of fluidsincluding gases where suitably arranged. Where it is required to blendtwo or more fluids where an additive is injected in very lowconcentration, it may be advantageous to use a combination of two ormore blending means 21 with the base fluid of one being the injectedadditive of another.

Referring now to FIG. 3, the injector 10 comprises an injector body 28,a cylinder 29 and a piston 30. The piston 30 and cylinder 29 arrangementis provided with seals which are not shown in the figure, but which maybe fixed in the injector body 28 and make sealing contact with thepiston 30 or link rod 40. The piston 30 is operable to reciprocate inthe cylinder 29 thereby increasing and decreasing the volume in thecylinder cavity 31. The injector 10 is provided with an inlet 34 whichcommunicates with the cylinder cavity 31 and is connected to an inletpipe feeding from the marker tank. The inlet 34 is provided with a checkvalve 35 which allows additive to enter the injector 10 but preventsflow in the opposite direction. The injector 10 is also provided with anoutlet 32 which communicates with the cylinder cavity 31 and which isconnected to the blender marker inlet 24 and marked oil delivery pipe 6.The outlet 32 is provided with a check valve 33 which allows additive toleave the cylinder cavity 31 but prevents flow in the oppositedirection. Reciprocating of the piston 30 will accordingly draw additivein through the inlet 34 and pump it out through the outlet 32. The checkvalves 33, 35 may of the known type where ball members seal againstseatings and are held against the seatings by the assistance of gravityand springs. Typically, the inlet check valve will have a metal to metalseating and be closed by gravity and the outlet check valve will have anelastomer seating and be closed by a spring.

The injector 10 is provided with a pneumatic actuator 36 whichreciprocates the injector piston 30. The actuator 36 comprises anactuator body 37, an actuator cylinder 38, an actuator piston 39 and alink rod 40. The actuator piston 39 and actuator cylinder 38 arrangementis provided with seals which are not shown in the figure. The injectorbody 28 and actuator body 37 may be made in one piece. The injectorpiston 30 is axially connected to the actuator piston 39 by theconnecting link rod 40 which may conveniently be arranged to allow somelateral movement. Each side of the actuator cavity 41 is connected to anactuator port 42 which communicates with a solenoid operated directionalcontrol valve 43 via restrictor arrangements 44 which control the speedof the actuator, such as restrictor and check valve arrangements 44. Therestrictor and check valve arrangements 44 allow air to freely enter thecylinder cavity 41 through the check valve but restricts its exit byforcing the air to pass through the restrictor valve. The solenoid valve43 is thus operable to control the reciprocation of the injector piston30 and the restrictor and check valve arrangements 44 are operable tocontrol the speed of the movement of the injector piston 30.

The actuator 36 is provided with a threaded stroke adjustment member 45which enters the actuator through a threaded hole and limits the strokeof the actuator piston 39 in one direction. The position of theadjustment member 45 can be varied by screwing it in or out of theactuator 36 and can be locked in position with a lock nut 46.

The accuracy of the injector can be affected by variations in operatingconditions. These variations include pressure variation in the oildelivery system. Some of this variation arises from the effect ofvarying flow rates and the resistance of the delivery hose, some fromthe elevation at which the delivery is being made in relation to thelevel of oil in the vehicle and some is due to the position of theoperator controlled valve at the delivery hose gun, which may be open orpartly closed during delivery. Other variations include the temperaturerelated viscosities of the oil and additive, which can affect backpressures and valve operation, and temperature effects on the resilienceof valve or piston seals and on friction effects in the valves oractuator.

When an injector is operating in a conventional manner the injectorcheck valves can remain in a dynamic situation during part of the cyclewhen, ideally, they should be firmly closed. Check valve dynamics aregenerally not well understood when the valves are operating rapidly andthe inaccuracies arising from this phenomenon are conventionally dealtwith by the process of calibration which compensates for losses acrossthe valves. The present invention provides that the injector cycle ofoperation is arranged to provide a deliberate preset delay prior to thesuction or delivery strokes to allow the valves to completely settle andarranging the injector size to be such that there is sufficient pumpingcapacity to allow these delays.

Variable flexing of piston seals may give rise to variations in thevolume of additive pumped on each stroke of the injector. This potentialsource of inaccuracy can be reduced by arranging the injector pump witha relatively high stroke to diameter ratio which reduces the sealsurface area in relation to the cylinder capacity. Increasing this ratioalso increases the relative accuracy of using end stops on the stroke tocontrol the volume as it minimises the volume in relation to the strokelength.

The injector pump and actuator are also arranged such that the forcedeveloped by the actuator is much greater than the force required by theinjector pump over the complete range of pressures possible in the basefluid delivery means. This will minimise the effects of variations indelivery line pressure on pump performance. It will also minimise theeffects of friction variations in the injector or actuator.

The injector stroke capacity is arranged relatively small, but not sosmall that the stroke rate is too high to allow sufficient time for thevalves to fully close as discussed earlier.

The actuator may be provided with restrictor and check valvearrangements which control the speed of the actuator in each direction.This prevents mechanical impact and shock on the end stops and otherparts, which reduces piston bounce and noise. It also reduces wear onthe end stops and helps to maintain consistency of stroke length overthe life of the injector. It additionally reduces hydraulic shock andinstability in the fluid systems which assists valve stability and helpsprolong the life of seals and components. High piston velocity cancreate undesirable high kinetic energy in the fluid, both within andoutside the injector, the dissipation of which can unsettle theoperation of the check valves and other moving parts when the pistonreaches the end of its stroke.

An example of an application of the invention is given below where theoil pump flow rate is 10 liters per second, the oil line operatingpressures vary from 0 bar to 9 bar, the additive concentration is 100parts per million and the regulated air supply to the actuator is 4 bar.An injector piston diameter of 6 mm is used with a stroke length of 50mm, giving a stroke volume of 1.41 ml. The average resulting time of theinjector is about 1.41 seconds per cycle. This time period is dividedbetween the valve settling before delivery, the delivery stroke, thevalve settling after delivery and the suction stroke. A longer period isallowed for the suction stroke than for the delivery stroke. The overalltime period is sufficient to satisfy the requirements for effectivevalve closure and the piston diameter to stroke ratio is adequately highto minimise the effects of seal flexing and accentuate the effectivenessof the end stop accuracy. An actuator piston diameter of 25 mm is usedwith a stroke of 50 mm matching the stroke of the injector piston. Thiscan be shown to cause the force capability of the actuator to be aboutseven times greater than the maximum resistance resulting from the oilline pressure acting on the injector which is adequate to minimise theeffects of variations in oil line pressure. In a properly designedsystem, this arrangement can readily provide accuracies within ±0.5%.

It will of course be understood that the invention is not limited to thespecific details described herein, which are given by way of exampleonly, and that various modifications and alterations are possible withinthe scope of the invention as defined in the appended claims.

What is claimed is:
 1. An apparatus for the addition of additivecomprisinga base fluid delivery means and a blending means having areceptacle or chamber, wherein mixing of additive and base fluid occurswithin the receptacle or chamber, and wherein the receptacle or chamberhasa base fluid inlet for receiving a portion of the fluid flowingthrough the delivery means, and an outlet for releasing from thereceptacle or chamber a mixture of base fluid and additive into thedelivery means downstream from the inlet, characterised in that additiveis added by injection in discrete amounts, and resistance to fluid flowcauses fluid flow in the receptacle or chamber to occur at rates orspeeds different to the base fluid delivery means, the apparatus beingoperable so that the slugging effect of additive injection in discreteamounts is reduced.
 2. An apparatus according to claim 1, comprising adiffusion chamber in which fluid flow occurs at a rate or speeddifferent to the base fluid delivery means and which has a base fluidinlet for receiving a portion of the fluid flowing through the deliverymeans, an inlet for receiving additive and a blender outlet forreleasing from the diffusion chamber a mixture of base fluid andadditive resulting from the combined flow or fluid flow mixing of thebase fluid and additive within the diffusion chamber.
 3. An apparatusaccording to claim 2, where the diffusion chamber is connected to thedelivery means by a base fluid inlet means and a blender outlet means,and where the base fluid inlet means or the blender outlet means or thediffusion means is restricted to regulate the flow of fluid passingthrough the diffusion chamber.
 4. An apparatus according to claim 2, inwhich the diffusion chamber is located in the stream of base fluid inthe delivery means, where a part of the diffusion chamber is restrictedto regulate the flow of fluid passing through the diffusion chamber. 5.An apparatus according to claim 2, wherein the apparatus furthercomprises a manifold located in the diffusion chamber where the manifoldis connected to the additive inlet and comprises a plurality of openingscommunicating with the diffusion chamber.
 6. An apparatus according toclaim 5, in which the diffusion chamber communicates with a deliverymeans, where additive is injected into the base fluid from a pluralityof openings along the manifold located in the diffusion chamber andconnected to the additive inlet so that additive injected into thediffusion chamber mixes with base fluid along the manifold to form anelongated body of mixed or partly mixed fluid, and the base fluid inletmeans or the blender outlet or part or parts of the diffusion chamberare restricted to regulate the flow and relative speed of fluid passingthrough the diffusion chamber so that there is overlap betweensuccessive elongated bodies of fluid passing through the diffusionchamber so that a substantially continuous stream of mixed fluid entersthe delivery means from the blender outlet of the diffusion chamber. 7.An apparatus according to any one of claim 5, wherein the manifold hasopenings on its upper surface so that additive is retained in themanifold.
 8. An apparatus according to claim 7, wherein the manifoldopenings are of small cross sectional area and of length which isrelatively long in proportion to their width, whereby scouring of themanifold is reduced or eliminated and whereby the speed of injection isreduced so that substantially even flow occurs through each of themanifold openings during injection.
 9. An apparatus according to claim2, wherein the diffusion chamber is positioned below the delivery meansso that the mixture of base fluid and additive is retained in thediffusion chamber.
 10. An apparatus according to claim 2, wherein thediffusion chamber is positioned at an inclined angle so that airentrapment is avoided in the diffusion chamber.
 11. An apparatusaccording to claim 1, wherein additive is injected into the base fluidat a plurality of positions along one or more paths of flow of the basefluid.
 12. An apparatus according to any one of claim 1, wherein mixingof additive and base fluid is increased in the blending means bygeometric means which creates turbulence within the blending means byutilising the flow energy of the additive when injected into the basefluid or by utilising the flow energy of the base fluid and additive bymeans of baffles or irregularities in the blending means.
 13. Anapparatus according to any one of claims 1, wherein the injection meansoperates in a cycle which includes a delivery stroke and the apparatusincludes means for restricting the speed of the delivery stroke wherebythe delivery stroke may be arranged to occur at a relatively slow speed.14. An apparatus according to any one of claim 1, wherein the blendingmeans is positioned below the delivery means so that the mixture of basefluid and additive is retained in the blending means.
 15. An apparatusaccording to claim 1, wherein the blending means is positioned at aninclined angle so that air entrapment is avoided in the blending means.16. An apparatus according to claim 1, wherein the blending means inletand outlet pipes are raised in the delivery means so that the ingress ofsludge or debris is avoided.
 17. An apparatus according to claim 1,wherein the blending means inlet is arranged with a much lowerresistance than the blender outlet so that the greater part of any flowsurges which take place during injection will occur through the blendinginlet means.
 18. An apparatus according to claim 1, wherein two or moreblending means are used in combination, with the base fluid of oneblending means being the additive of another blending means.